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1、编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第1页 共1页附录附录1英文原文Rolling Contact BearingsThe concern of a machine designer with ball and roller bearings is fivefold as follows:(a) life in relation to load; (b) stiffness,ie.deflections under load; (c) friction; (d) wear; (e) noise. For moderate loads and speeds the
2、correct selection of a standard bearing on the basis of a load rating will become important where loads are high,although this is usually of less magnitude than that of the shafts or other components associated with the bearing. Where speeds are high special cooling arrangements become necessary whi
3、ch may increase fricitional drag. Wear is primarily associated with the introduction of contaminants,and sealing arrangements must be chosen with regard to the hostility of the environment. Because the high quality and low price of ball and roller bearing depends on quantity production,the task of t
4、he machine designer becomes one of selection rather than design. Rolling-contact bearings are generally made with steel which is through-hardened to about 900HV,although in many mechanisms special races are not provided and the interacting surfaces are hardened to about 600HV. It is not surprising t
5、hat,owing to the high stresses involved,a predominant form of failure should be metal fatigue, and a good deal of work is based on accept values of life and it is general practice in bearing industry to define the load capacity of the bearing as that value below which 90 percent of a batch will exce
6、ed life of one million revolutions. Notwithstanding the fact that responsibility for basic design of ball and roller bearings rests with the bearing manufacturer, the machine designer must form a correct appreciation of the duty to be performed by the bearing and be concerned not only with bearing s
7、election but with the conditions for correct installation. The fit of the bearing races onto the shaft or onto the housings is of critical importance because of their combined effect on the internal clearance of the bearing as well as preserving the desired degree of interference fit. Inadequate int
8、erference can induce serious trouble from fretting corrosion. The inner race is frequently located axially by against a shoulder. A radius at this point is essential for the avoidance of stress concentration and ball races are provided with a radius or chamfer to follow space for this.Where life is
9、not the determining factor in design, it is usual to determine maximum loading by the amount to which a bearing will deflect under load. Thus the concept of static load-carrying capacity is understood to mean the load that can be applied to a bearing, which is either stationary or subject to slight
10、swiveling motions, without impairing its running qualities for subsequent rotational motion. This has been determined by practical experience as the load which when applied to a bearing results in a total deformation of 0.0025mm for a ball 25mm in diameter. The successful functioning of many bearing
11、s depends upon providing them with adequate protection against their environment, and in some circumstances the environment must be protected from lubricants or products of deterioration of the bearing design. Moreover, seals which are applied to moving parts for any purpose are of interest to tribo
12、logists because they are components of bearing systems and can only be designed satisfactorily on basis of the appropriate bearing theory. Notwithstanding their importance, the amount of research effort that has been devoted to the understanding of the behavior of seals has been small when compared
13、with that devoted to other aspects of bearing technology.Lathes Lathes are widely used in industry to produce all kinds of machined parts. Some are general purpose machines, and others are used to perform highly specialized operations. Engine lathesEngine lathes, of course, are general-purpose machi
14、ne used in production and maintenance shop all over the the world. Sized ranger from small bench models to huge heavy duty pieces of equipment. Many of the larger lathes come equipped with attachments not commonly found in the ordinary shop, such as automatic shop for the carriage.Tracer or Duplicat
15、ing LathesThe tracer or duplicating lathe is designed o produce irregularly shaped parts automatically. The basic operation of this lathe is as fallows. A template of either a flat or three-dimensional shape is placed in a holder. A guide or pointer then moves along this shape and its movement contr
16、ols that of the cutting tool. The duplication may include a square or tapered shoulder, grooves, tapers, and contours. Work such as motor shafts, spindles, pistons, rods, car axles, turbine shafts, and a variety of other objects can be turned using this type of lathe.Turret LathesWhen machining a complex workpiece on a general-purpose lathe, a great deal of time is spent changing and adjusting the several tools that are needed t
